From patchwork Tue Mar 28 16:13:06 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 13191337 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C7741C6FD18 for ; Tue, 28 Mar 2023 16:13:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232753AbjC1QNi (ORCPT ); Tue, 28 Mar 2023 12:13:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49618 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232747AbjC1QNf (ORCPT ); Tue, 28 Mar 2023 12:13:35 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 178BFE3B4 for ; Tue, 28 Mar 2023 09:13:26 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 948FBB81DA5 for ; Tue, 28 Mar 2023 16:13:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5F5EFC4339E; Tue, 28 Mar 2023 16:13:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1680020003; bh=IMnzmusWqH/wdAAywJGvV4jW/PNRucB2FHw5lIG7LRk=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=Zkuf1TjwjolI/E2x2I1c63SG3BGVT9VxWoOC1C4XX+dc0E15/f37tvYqGNHXaZJpE 30hWG6ut5M59VLGJKcJtIpK4GqN1hU+vYxLtLdKTCgDVL3gMLK9XNMh/M8f6ht4XN5 3A51lMDSDj8yMssa4Wh5AYzmZVozIy9rUomP0VPwq4wQx+1iFBTTIZ8jkwPxC678Hl kn6pElFyChl1QiBVKmd4GLYaXxWFuCPUDIDiOAGiCiJ5ldrf1lnKOKmB4OaJIr/fyc vJM6PJo3f+SGZzSlhiskvGUtn0IL7+Ohm6MJJrlLnqw40km4XlolQdE+4lH9d+X0SC inx1XRgWuYU3A== From: Christian Brauner Date: Tue, 28 Mar 2023 18:13:06 +0200 Subject: [PATCH v2 1/5] fs: add path_mounted() MIME-Version: 1.0 Message-Id: <20230202-fs-move-mount-replace-v2-1-f53cd31d6392@kernel.org> References: <20230202-fs-move-mount-replace-v2-0-f53cd31d6392@kernel.org> In-Reply-To: <20230202-fs-move-mount-replace-v2-0-f53cd31d6392@kernel.org> To: Al Viro , Seth Forshee Cc: linux-fsdevel@vger.kernel.org, Christian Brauner X-Mailer: b4 0.13-dev-00303 X-Developer-Signature: v=1; a=openpgp-sha256; l=4051; i=brauner@kernel.org; h=from:subject:message-id; bh=IMnzmusWqH/wdAAywJGvV4jW/PNRucB2FHw5lIG7LRk=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMaQoC8l/e1+5jis7vVf3d2H/1KKMGbefxNUHRiZNDGxK+C+p +PRWRykLgxgXg6yYIotDu0m43HKeis1GmRowc1iZQIYwcHEKwETKlzH8ZFTaVPb7jK/DgrQpz1R41j fZZTX2yFyrl7uevCW/Tbf2PMNfEbZpnTox6fN3/FXmOvzVfG/xd3lDTz6+tfuOXfQ6NjWGHQA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Add a small helper to check whether a path refers to the root of the mount instead of open-coding this everywhere. Signed-off-by: Christian Brauner Reviewed-by: Seth Forshee (DigitalOcean) --- fs/namespace.c | 36 ++++++++++++++++++++++++------------ 1 file changed, 24 insertions(+), 12 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index bc0f15257b49..154569fd7343 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1767,6 +1767,19 @@ bool may_mount(void) return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); } +/** + * path_mounted - check whether path is mounted + * @path: path to check + * + * Determine whether @path refers to the root of a mount. + * + * Return: true if @path is the root of a mount, false if not. + */ +static inline bool path_mounted(const struct path *path) +{ + return path->mnt->mnt_root == path->dentry; +} + static void warn_mandlock(void) { pr_warn_once("=======================================================\n" @@ -1782,7 +1795,7 @@ static int can_umount(const struct path *path, int flags) if (!may_mount()) return -EPERM; - if (path->dentry != path->mnt->mnt_root) + if (!path_mounted(path)) return -EINVAL; if (!check_mnt(mnt)) return -EINVAL; @@ -2367,7 +2380,7 @@ static int do_change_type(struct path *path, int ms_flags) int type; int err = 0; - if (path->dentry != path->mnt->mnt_root) + if (!path_mounted(path)) return -EINVAL; type = flags_to_propagation_type(ms_flags); @@ -2646,7 +2659,7 @@ static int do_reconfigure_mnt(struct path *path, unsigned int mnt_flags) if (!check_mnt(mnt)) return -EINVAL; - if (path->dentry != mnt->mnt.mnt_root) + if (!path_mounted(path)) return -EINVAL; if (!can_change_locked_flags(mnt, mnt_flags)) @@ -2685,7 +2698,7 @@ static int do_remount(struct path *path, int ms_flags, int sb_flags, if (!check_mnt(mnt)) return -EINVAL; - if (path->dentry != path->mnt->mnt_root) + if (!path_mounted(path)) return -EINVAL; if (!can_change_locked_flags(mnt, mnt_flags)) @@ -2775,9 +2788,9 @@ static int do_set_group(struct path *from_path, struct path *to_path) err = -EINVAL; /* To and From paths should be mount roots */ - if (from_path->dentry != from_path->mnt->mnt_root) + if (!path_mounted(from_path)) goto out; - if (to_path->dentry != to_path->mnt->mnt_root) + if (!path_mounted(to_path)) goto out; /* Setting sharing groups is only allowed across same superblock */ @@ -2858,7 +2871,7 @@ static int do_move_mount(struct path *old_path, struct path *new_path) if (old->mnt.mnt_flags & MNT_LOCKED) goto out; - if (old_path->dentry != old_path->mnt->mnt_root) + if (!path_mounted(old_path)) goto out; if (d_is_dir(new_path->dentry) != @@ -2940,8 +2953,7 @@ static int do_add_mount(struct mount *newmnt, struct mountpoint *mp, } /* Refuse the same filesystem on the same mount point */ - if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && - path->mnt->mnt_root == path->dentry) + if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && path_mounted(path)) return -EBUSY; if (d_is_symlink(newmnt->mnt.mnt_root)) @@ -3920,11 +3932,11 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, if (new_mnt == root_mnt || old_mnt == root_mnt) goto out4; /* loop, on the same file system */ error = -EINVAL; - if (root.mnt->mnt_root != root.dentry) + if (!path_mounted(&root)) goto out4; /* not a mountpoint */ if (!mnt_has_parent(root_mnt)) goto out4; /* not attached */ - if (new.mnt->mnt_root != new.dentry) + if (!path_mounted(&new)) goto out4; /* not a mountpoint */ if (!mnt_has_parent(new_mnt)) goto out4; /* not attached */ @@ -4127,7 +4139,7 @@ static int do_mount_setattr(struct path *path, struct mount_kattr *kattr) struct mount *mnt = real_mount(path->mnt); int err = 0; - if (path->dentry != mnt->mnt.mnt_root) + if (!path_mounted(path)) return -EINVAL; if (kattr->mnt_userns) {